Field devices are used in a variety of process plants, such as chemical refinery plants and pharmaceutical manufacturing plants, to measure, monitor, and control parameters of the process. A field device may be a control device, such as a valve controller or actuator, a process variable transmitter, such as a process pressure transmitter, et cetera or any other device that may affect or be affected by a value associated with the process.
Many field devices are so-called “smart” field devices in that they are capable of digital communication and typically include a microprocessor or other suitable processing circuitry. Smart field devices store and digitally transmit detailed information that may be specific to the field device itself, including calibration, diagnostic information, maintenance information, configuration information, et cetera. All of this information can be transmitted in addition to the process information. Some field devices may store and transmit the units in which the device is measuring, an indication regarding whether the device is operating properly, the maximum and minimum measurement ranges of the device, diagnostic information, et cetera. In fact, many smart field devices are able to perform operations on themselves, such as self diagnostics and/or self calibration. Smart field devices typically communicate digitally in accordance with a process standard communication protocol. Examples of such protocols include the Highway Addressable Remote Transducer (HART®) protocol, the FOUNDATION™ Fieldbus protocol, and others.
Communication with a specific smart field device is generally performed in accordance with the device's communication protocol. Some process standard communication protocols, such as FOUNDATION™ Fieldbus and HART®, use a device description (DD) that is written in accordance with a device description language. A device description language (DDL) is a human-readable language that provides a protocol for describing the capabilities of a smart field device, such as the data available from the field device, the meaning of the data associated with and retrieved from the smart field device, as well as methods or procedures that can be used with the smart field device. The format for communicating with the field device to obtain data and user interface information is also generally set forth in the device description.
A device description (DD) is a file written in accordance with a communication protocol or a particular DDL which specifies all the information available regarding a specific smart field device. Device descriptions for smart field devices typically specify five categories of information including: 1) identification of the parameters and/or properties associated with the device, including the types of data defining the parameters and/or properties (such as whether the parameters and/or properties are variables, arrays, or records and the units associated with each); 2) commands necessary for communication with the field device including information regarding how to send messages to and receive messages from the field device; 3) user interface data such as menus and displays which logically group parameter and/or property-related data; 4) methods or procedures to be run by a host device in relation to the smart field device, such methods may include providing information to a user in the form of instructions and/or sending messages to the smart field device to implement, for example, a diagnostic or calibration routine on the field device; and 5) utility information such as device-description writer-defined groupings of parameter or properties to be used in connection with the parameter, command, user interface, and method information.
In order to develop a device description source file for a smart field device, a developer or manufacturer typically uses the device description language for the communication protocol associated with that field device to describe core or essential characteristics of the field device. Additionally, the developer may provide group-specific and/or vendor-specific definitions relative to functions and special features of the field device. The developed device description source file is then compiled into a machine-readable device description object file using, for example, a tokenizer. Device description object files are typically provided to a user by the device manufacturer or a third-party developer to be stored in a host system such as a field device management system or a handheld field maintenance tool. The host system uses the device description object file for a smart field device to decode and define a complete description of the interface with the smart field device.
Some smart field devices, such as FOUNDATION™ Fieldbus devices which may include temperature, pressure, level, and flow instruments as well as final control elements including, but not limited to, valves use a technology known as “electronic device description” to provide host systems such as a distributed control system, programmable logic controller, or asset management software located in both fixed and portable platforms with information on the full capabilities of the smart field device and the ways in which the field device and those capabilities may be accessed. Loss or failure of a smart field device can have severe consequences on the process including reduced quality, loss of production, unintended emissions, and/or compromised safety for plant personnel.
Manufacturers of smart field devices sometimes issue new revisions of device hardware and/or software to correct problems or enhance functionality. These new revisions sometimes require a different electronic device description to describe the device capabilities and the manner in which those capabilities may be accessed. Although the device is revised, the device model numbers generally do not change. Thus, an end user may have several devices with the same model number but with different revision levels. To access and use device functionality, an electronic device description appropriate for each specific device revision must be installed on the host.
Traditionally, electronic device descriptions can be obtained from several sources including vendor websites and foundations, such as the Fieldbus foundation. These electronic device descriptions are sometimes shipped with the field devices on a CD or other computer-readable media. If the user of the field device is not aware that a specific device has had a revision and that a new electronic device description is needed to access and use device functionality, the user may fail to obtain and install the appropriate electronic device description on the host system. If this happens, the user may find that a smart field device cannot be set up, commissioned, configured, or otherwise initiated. Field devices are frequently located in remote locations such as offshore drilling platforms and other locations where internet access is not available. This prevents the user from easily obtaining electronic device descriptions from traditional sources such as a vendor or internet website. This can result in a number of undesirable consequences.